It is known from the art conditioning cylinders employed in the mixing, steam conditioning, drying and applying of flowing material to a bulk material, for example, tobacco, to be treated. Such cylinders are placed with its input end elevated in relation to the output end and are rotated around the longitudinal geometric axis usually at about fifteen revolutions per minute. Thus, the material to be treated enters one end of the cylinder (inlet end) and, given that the cylinder is in tilted position, by force of gravity the material moves and leaves already treated through the other end (outlet end) in a continuous flow process.
One of the materials that is sensitive to mechanical stress is pre-treated tobacco, for example, cured tobacco or expanded tobacco, which presents low moisture content and require reconditioning. Consequently, it is necessary to increase the moisture content of such materials to a value within the range of 12 a 16%, usually by the employment of water steam. This increase in moisture content makes the tobacco more flexible and less liable to break during subsequent process operations for the manufacture of tobacco based products. However, it is logical that the moisture operation should be performed in conditions which ensure a uniform distribution of moisture in the material and imply minimum degradation of such material.
Generally, conditioning processes and other tobacco treatments (such as, for example, fixing added ingredients, volatilizing undesired substances etc.) require a temperature increase to render the treatment more effective. Such heating is one of the many conditions that can lead to unwanted changes in tobacco physical characteristics, for example, fragmentation.
For example, in patent U.S. Pat. No. 6,286,515, it is disclosed a moistening cylinder comprising (i) a first rotating cylinder having an input end and an output end and a plurality of blades extending radially from the outer surface of the first cylinder; (ii) a second rotating cylinder also having an input end and an output end and a plurality of blades extending radially from the inner surface of the second cylinder, wherein both cylinders are arranged coaxially with the first cylinder in the interior of the second cylinder, defining an annular space where the material is treated; (iii) a motor for driving both coaxial cylinders and tubes placed in the annular space for moisture introduction. Such apparatus, however, has elements that can damage the material being treated, for example, the two set of blades which, jointly with the rotation movement of the cylinders, cause continuous falls of the material from a set of blades to the other set, implying in damage to the material sensitive to mechanical stress.
Therefore, is evident the need of an apparatus which allows tobacco treatment or another bulk material sensitive to mechanical stress, in an efficient manner without, however, impairing the integrity of the material being treated.